Abstract: With the development of mobile communication technology and the popularization of internet of vehicles (IoV) technology, in-vehicle OTA (Over-the-Air) technology emerges as the times require. In-vehicle OTA technology can realize remote repair and update of in-vehicle software system, reduce vehicle maintenance costs and improve car owners' experience. This paper described the OTA technology system architecture, upgrade strategy and technical route. It summarized the research progress and current situation of in-vehicle OTA technology, analyzed and explained the three key technologies in remote flashing of in-vehicle software, such as differential upgrade, rollback reflash and safety mechanism, and discussed the upgrade scheme of in-vehicle OTA system respectively from the aspects of design principles, update modes and flashing process. This paper looked into the future development trends of in-vehicle OTA technology from two aspects: new requirements for vehicle software upgrade and 5G Internet of Vehicles technology.